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Accurately estimating annual average daily traffic (AADT) on minor roads is essential for assessing traffic-related air pollution (TRAP) exposure, particularly in areas where most people live. Our study assessed the direct and indirect external validity of three methods used to estimate AADT on minor roads in Melbourne, Australia. We estimated the minor road AADT using a fixed-value approach (assuming 600 vehicles/day) and linear and negative binomial (NB) models. The models were generated using road type, road importance index, AADT and distance of the nearest major road, population density, workplace density, and weighted road density. External measurements of traffic counts, as well as black carbon (BC) and ultrafine particles (UFP), were conducted at 201 sites for direct and indirect validation, respectively. Statistical tests included Akaike information criterion (AIC) to compare models' performance, the concordance correlation coefficient (CCC) for direct validation, and Spearman's correlation coefficient for indirect validation. Results show that 88.5% of the roads in Melbourne are minor, yet only 18.9% have AADT. The performance assessment of minor road models indicated comparable performance for both models (AIC of 1,023,686 vs. 1,058,502). In the direct validation with external traffic measurements, there was no difference between the three methods for overall minor roads. However, for minor roads within residential areas, CCC (95% confidence interval [CI]) values were −0.001 (−0.17; 0.18), 0.47 (0.32; 0.60), and 0.29 (0.18; 0.39) for the fixed-value approach, the linear model, and the NB model, respectively. In the indirect validation, we found differences only on UFP where the Spearman's correlation (95% CI) for both models and fixed-value approach were 0.50 (0.37; 0.62) and 0.34 (0.19; 0.48), respectively. In conclusion, our linear model outperformed the fixed-value approach when compared against traffic and TRAP measurements. The methodology followed in this study is relevant to locations with incomplete minor road AADT data. [Display omitted] • Minor roads contribute to air pollution but their traffic volume is largely unknown. • Direct external validation of models showed good performance in residential areas. • Indirect external validation of ultrafine particle models showed good performance. • The models can estimate minor roads' traffic volume in large cities. • The method is relevant to locations with incomplete minor road traffic volume data. [ABSTRACT FROM AUTHOR]

In order to successfully colonise the urban environment, birds must be able tolerate pedestrian and vehicle proximity, because exhibiting a strong fleeing response each time that a harmless traffic stimulus is encountered would be maladaptive. We examined whether a native 'urban adapter', the Australian magpie (Cracticus tibicen), varied in its tolerance of human approach and a simulated vehicular traffic sound in urban Melbourne, Australia as a function of pedestrian or vehicular traffic volume in the local area. The flight initiation distance (FID) paradigm and presentation of a potentially startling sound stimulus (SSS) were used to measure the magpies' boldness in areas with differing traffic volumes. Magpies in areas with relatively high pedestrian traffic volumes exhibited a shorter FID to, and retreated a shorter distance from, an approaching human than conspecifics experiencing relatively low volumes of pedestrian traffic. Magpies in areas with a relatively high vehicular traffic volume were less likely to flee from a SSS than conspecifics in areas with little or no vehicular traffic. Habituation to human disturbance and/or adjustment of anti-predator effort seem the most likely explanations for these disparities and suggest that magpies have considerable behavioural flexibility. The ability to tolerate high volumes of traffic and the associated noise allows magpies to use: (a) ecologically suitable habitat adjoining city roads with heavy vehicular traffic and (b) urban areas with many pedestrians and consequently much human food waste, which the birds exploit. [ABSTRACT FROM AUTHOR]